1. Field of the Invention
The present invention relates to an improved method for manufacturing sliders. More particularly, the invention relates to an improved method for removing unwanted alumina from the alumina overcoat on a slider.
2. Description of the Background Art
Digital magnetic recording devices for data storage generally comprise a thin film magnetic recording disk and a head or transducer which is moved above the surface of the rotating disk to electromagnetically read and write information on the disk. Advanced thin film magnetic recording disks generally comprise a rigid substrate, a magnetic layer such as a cobalt-based metal alloy, a protective amorphous carbon layer and a lubricant layer, such as a perfluoropolyether disposed on the carbon overcoat.
During operation of the disk drive system, an actuator mechanism moves the magnetic transducer to a desired radial position on the surface of the rotating disk where the head electromagnetically reads or writes data. Usually, the head is integrally mounted in a carrier or support referred to as a "slider". The slider generally consists of two contiguous portions, i.e., a slider portion and a head portion formed on an end face of the slider portion. Typically, the end face of the slider will constitute the slider trailing edge when the slider is suspended adjacent to a rotating recording disk.
The slider portion, which constitutes the bulk of the thin film head slider, is made of a ceramic material such as Al.sub.2 O.sub.3 --TiC or another suitable material. The head portion of the slider typically is a thin layer of alumina formed on the trailing edge face of the slider portion in which the magnetic portion of the head is embedded.
A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.
Typically, a slider is formed with an aerodynamic pattern of protrusions (air bearing design) on its air bearing surface (ABS) which enable the slider to fly at a constant height close to the disk during operation of the disk drive.
The recording density of a magnetic disk drive is dependent on the distance between a transducer and the magnetic media. One goal of air bearing slider design is to "fly" a slider as closely as possible to a magnetic medium while avoiding physical impact with the medium. Smaller spacings, or "fly heights", are desired so that the transducer can distinguish between the varying magnetic fields emanating from closely spaced regions on the disk.
However, the benefit of a closer spacing is constrained by the adverse effect on the mechanical reliability. As the distance between the slider and the disk decreases, as it does with every generation of storage device, the probability of contact between the two increase which causes wear on both contacting surfaces that could ultimately lead to loss of data.
Because sliders fly with a positive pitch, the point on the slider that has the highest probability of coming in contact with the disk is the alumina overcoat on the trailing surface. The probability of contact between the slider and disk increase when the alumina on the trailing edge protrudes above the air bearing surface of the slider. Referring to FIG. 1, there is shown a slider 10 comprising slider portion 12 and head portion 14 together forming the air bearing surface 16 of the slider. The head portion 14 of the slider comprises an alumina undercoat 20, read and write head elements 22, 24 and 26, and the alumina overcoat 28. Referring to FIG. 2, there is shown an alumina overcoat 28 of slider 10 protruding above the ABS surface of slider portion 12, thereby substantially increasing the probability of contact with the disk. Protrusion of the overcoat of alumina can result from (i) lapping of the air bearing surface (ABS) or (ii) from operation of the slider. During operation of the slider, there is an increase in the temperature of the slider and the differences in coefficient of thermal expansion of the slider components can result in protrusion of the alumina overcoat.
In the manufacturing of sliders, a large number of sliders are fabricated from a single wafer having rows of the magnetic transducers deposited simultaneously on the wafer surface using semiconductor-type process methods. In one process embodiment, after deposition of the heads is complete, the wafer is cut into four quadrants. Each quadrant is then bonded to a lapping fixture and lapped on a lapping plate to provide accurate head dimensions. After lapping, single row bars of sliders are cut from the wafer quadrant. These row bars may then be lapped again on the ABS, and the ABS design is etched in each slider using art-known lithographic techniques. Lastly, the row bars are adhered to suitable tape; and each bar is diced, i.e., separated with a diamond-cut saw into individual sliders, each having a magnetic head terminating at the ABS. Each slider is then cleanly removed from the tape, inspected to insure operability of the magnetic head, and attached to an actuator for use in a magnetic disk drive.
Unfortunately, as discussed above, the lapping process can result in an alumina overcoat protrusion which will increase the probability of contact between the disk and slider. Acid and bases are known to etch alumina. However, their use to etch away the overcoat protrusion of sliders results in batch to batch variations of overcoat protrusion height due to variations of etch rate and non-uniform removal of alumina overcoat protrusion. Therefore, there still is a need in the art for a slider manufacturing process which results in sliders without alumina overcoat protrusion.
It is, therefore, an object of the present invention to provide an improved method for the manufacturing of magnetic sliders. Other objects and advantages will become apparent from the following disclosure.